This application is based on patent application No. 9-155318 filed in Japan, the contents of which is hereby incorporated by reference.
This invention relates to an image pickup apparatus, particularly to an electronic camera which can photograph a focused image of an object over its entirety by dividing a light image of the object into a plurality of sub-images and exposing each of the sub-images while focusing the same.
There have been known cameras in which a light image of an object is divided into a plurality of sub-images and these sub-images are successively exposed on a photosensitive member such as image sensor to photograph an entirety of the object image. In such a camera, a CCD line image sensor or a line image sensor comprising CCD (Charge Coupled Device) is disposed at a position different from an optical axis of a taking lens; a mirror for reflecting the light image onto a sensing surface of the line image sensor is disposed on the optical axis of the taking lens in such a manner that an angle of a reflected surface of the mirror with respect to the sensing surface of the CCD line image sensor is variable; and the light image of the object is scanned (sensed) by the CCD line image sensor by rotating the mirror and varying the reflected angle thereof, thereby photographing the entire image of the object. Hereinafter, a camera of this type is referred to as a xe2x80x9cmirror scan typexe2x80x9d camera.
FIG. 33 is a schematic construction diagram of an image pickup and optical system of a mirror scan type camera.
In FIG. 33, a board (object) 101 is disposed in parallel with a lens plane and in front of a taking lens 100 on an optical axis L. A mirror 102 is disposed rotatable at a rear position of the taking lens 100 on the optical axis L. A line image sensor 103 is arranged above the mirror 102.
The mirror 102 is rotatable about a rotational axis which perpendicularly intersects the optical axis L. A reflected surface of the mirror 102 opposes to the board 101 and the line image sensor 103. When an angle xcfx86 which is defined by the optical axis L and the mirror 102 is set at xcfx86=xcfx861, xcfx862, xcfx863, points A, B, C on the board 101 are respectively projected on the sensing surface of the line image sensor 103.
In other words, when the mirror 102 is rotated from the position xcfx861 to xcfx863, the line image sensor 103 relatively scans the board 101 from the position A to the position C. Accordingly, as the line image sensor 103 picks up the image of the object 101 in synchronism with the rotation of the mirror 102 which rotates at a given speed, a slender image (sub-image) is successively scanned, and synthesizing these sub-images enables reading of the entire image of the board 101 from the position A to the position C.
The above image pickup system of mirror scan type has the following problem. Since a distance (length of optical path) from the taking lens 100 to the sensing surface of the line image sensor 103 is varied in accordance with the rotation of the mirror 102, the likelihood cannot be avoided that an unfocused sub-image is read during the scanning, resulting in picking up an unfocused image as a whole.
Photographing an image with its entirety in a focused state is in great need depending on the situation, particularly, in a case where giving information (such as characters and figures are drawn on a white board) is essential than showing a graphic image. Further, also in taking a landscape photo, there is a necessity of focusing an entire image, e.g., in the case where plural persons are arranged in a field with different object distances from one another.
In the above cases, there has been proposed a photographing method in which the depth of field is increased as much as possible by reducing the exposure amount as much as possible to obtain a seemingly focused photographed image. However, this photographing method has the limit on reliability in the following cases. For example, in the case where an entirety of a building is photographed from an oblique direction, an object distance distribution within a field greatly varies. Further, in photographing an object inside a room, an exposure light amount to the object is not sufficient. In either case, a desired exposure amount cannot be obtained owing to various factors such as the composition of the photographed image and the condition of photographing, resulting in an unfocused image as a whole.
It is an object of the present invention to provide an image pickup apparatus which has overcome the problems residing in the prior art.
It is another object of the present invention to provide an image pickup apparatus which can pick up a focused object image over its entirety with a simplified construction.
According to an aspect of the invention, an image pickup apparatus comprises: a photosensitive member; a light image introducer which introduces respective light images of divided parts of an object part-by-part onto the photosensitive member, the light image introducer including a taking lens; a distance information generator which generates distance information for each divided part of the object, the distance information generator including a distance detector which detects a distance to the object; and a lens driver which drives the taking lens based on generated distance information.
According to another aspect of the invention, an image pickup apparatus comprises: an image sensor; a light image introducer which introduces respective light images of divided parts of an object part-by-part onto the image sensor, the light image introducer including a taking lens; a distance information generator which generates distance information for each divided part of the object, the distance information generator including a distance detector which detects a distance to the object; a lens driver which drives the taking lens based on generated distance information; and an image corrector which corrects output of the image sensor to eliminate an image distortion caused by an oblique image pickup.